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Starting a module with Module::Starter</title>
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<h1>

Starting a module with Module::Starter
</h1>




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<p>Starting a new module can be a lot of work.  A good module should have
a build system, documentation, a test suite, and numerous other bits
and pieces to assist in its easy packaging and development.  These are
useful even if we never release our module to CPAN.</p>
<p>Setting this up can be a lot of work, especially if you've never done
it before.  While the <code>h2xs</code> tool that comes with Perl will do some
of this for you, it's showing its age, and doesn't allow us to take
advantage of recent tools.  We want to spend our time writing code,
not trying to decode our build system.</p>
<p>That's where <code>Module::Starter</code> comes in handy.  It provides
a simple, command-line tool to create a skeleton module quickly and
easily.</p>

<!-- END_SUMMARY -->

<h2>Using module-starter</h2>
<p>Before we can build our module, we need to install <code>Module::Starter</code>
from the CPAN.   <code>Module::Starter</code> allows us to choose from a variety
of build frameworks, from the aging <code>ExtUtils::MakeMaker</code> to
<code>Module::Install</code> and <code>Module::Build</code>.  While <code>ExtUtils::MakeMaker</code>
comes standard with Perl, you may need to install the other build
frameworks.  At Perl Training Australia we generally use
<code>Module::Install</code>.</p>
<p>Creating a module with <code>Module::Starter</code> couldn't be easier.  On
the command line we simply write:</p>
<pre>
    module-starter --module=My::Module --author=&quot;Jane Smith&quot;
        --email=jane.smith@example.com --builder=Module::Install</pre>
<p>The module name, author, and e-mail switches are all required.
We've used the optional <code>--builder</code> switch to specify we want
to use <code>Module::Install</code> as our build-system, instead of
the default <code>ExtUtils::MakeMaker</code>.</p>
<p>Once this is done, you should have a <code>My-Module</code> directory with a
skeleton module inside.</p>
<p>
</p>
<h2>A skeleton tour</h2>
<p>If you've never created a module before, or you've been making them
by hand, then it's nice to take a look at what you get for your
<code>Module::Starter</code> skeleton.</p>
<pre>
    $ ls -la</pre>
<pre>
    total 8
    drwxr-xr-x   4 pjf pjf    0 Jul  4 16:59 .
    drwxr-xr-x  51 pjf pjf    0 Jul  4 16:59 ..
    -rw-r--r--   1 pjf pjf   96 Jul  4 16:59 .cvsignore
    -rw-r--r--   1 pjf pjf  109 Jul  4 16:59 Changes
    -rw-r--r--   1 pjf pjf   90 Jul  4 16:59 MANIFEST
    -rw-r--r--   1 pjf pjf  183 Jul  4 16:59 Makefile.PL
    -rw-r--r--   1 pjf pjf 1378 Jul  4 16:59 README
    drwxr-xr-x   3 pjf pjf    0 Jul  4 16:59 lib
    drwxr-xr-x   2 pjf pjf    0 Jul  4 16:59 t</pre>
<p>Let's look at each of these files in turn:</p>
<dl>
<dt><strong>.cvsignore</strong></dt>

<dd>
<p><code>Module::Starter</code> assumes you'll be using CVS for revision control, and
provides a <em>.cvsignore</em> file with the names of files that are auto-generated
and not to be tracked with revision control.  At Perl Training Australia
we use git for new projects, and so we rename this to <em>.gitignore</em>.</p>
</dd>
<dt><strong>Changes</strong></dt>

<dd>
<p>This is a human-readable file tracking module revisions and changes.
If you're going to release your code to the CPAN, it's essential for
your users to know what has changed in each release.  Even if you're
only using your code internally, this is a good place to document the
history of your project.</p>
</dd>
<dt><strong>MANIFEST</strong></dt>

<dd>
<p>The <em>MANIFEST</em> file tracks all the files that should be packaged when
you run a <code>make tardist</code> to distribute your module.  Normally it
includes your source code, any file needed for the build system,
a <em>META.yml</em> that contains module meta-data (usually auto-generated
by your build system), tests, documentation, and anything else that
you want your end-user to have.</p>
</dd>
<dd>
<p>If you don't want to manually worry about adding entries to the
<em>MANIFEST</em> file yourself, most build systems (including
<code>Module::Install</code>) allow you to write <code>make manifest</code> to auto-generate
it.  For this to work, you'll want to make a <em>MANIFEST.skip</em> file
which contains filenames and regular expressions that match files
which should be excluded from the <em>MANIFEST</em>.</p>
</dd>
<dt><strong>Makefile.PL</strong></dt>

<dd>
<p>This is the front-end onto our build system.  When we wish to build,
test, or install our module, we'll always invoke <em>Makefile.PL</em> first:</p>
</dd>
<dd>
<pre>
    perl Makefile.PL
    make
    make test
    make install</pre>
</dd>
<dd>
<p>Most build systems will provide a <code>make tardist</code> target for
building a tarball of all the files in our <em>MANIFEST</em>, a
<code>make disttest</code> for making sure our tests work with only the
<em>MANIFEST</em> listed files, and <code>make clean</code> and <code>make distclean</code>
targets for clearing up auto-generated files, including those
from the build system itself if a <code>make distclean</code> is run.</p>
</dd>
<dd>
<p>You'll almost certainly wish to customise your <em>Makefile.PL</em> a little,
especially if your module has dependencies.  You'll want to consult
your build system documentation for what options you can uses.  For
<code>Module::Install</code> this documentation can be found at
<a href="http://search.cpan.org/perldoc?Module::Install">http://search.cpan.org/perldoc</a>.</p>
</dd>
<dt><strong>README</strong></dt>

<dd>
<p>The <em>README</em> file should contain basic information for someone thinking
of installing your module.  Mentioning dependencies, how to build, and
how to find/report bugs are all good things to mention in the <em>README</em>
file.  Some systems (including the CPAN) will extract the <em>README</em>
and make it available separate from the main distribution.</p>
</dd>
<dt><strong>lib/</strong></dt>

<dd>
<p>The <em>lib/</em> directory will contain your skeleton module, and is
where you'll be doing much of your work.  <code>Module::Starter</code> will
have already added some skeleton documentation, a version number,
and some skeleton functions.</p>
</dd>
<dd>
<p>You can add more modules to the <em>lib/</em> directory if you wish.  Splitting
a very large module into smaller, logical pieces can significantly
improve maintainability.</p>
</dd>
<dt><strong>t/</strong></dt>

<dd>
<p>The <em>t/</em> directory contains all the tests that will be executed
when you run a <code>make test</code>.  By default, <code>Module::Starter</code> will
provide some simple tests to ensure that your module compiles, that
you'll filled in relevant sections of the boilerplate documentation,
and that your documentation covers all your subroutines and doesn't
contain any syntax errors.</p>
</dd>
<dd>
<p>If you're new to testing in Perl, then you should start by reading
the <code>Test::Tutorial</code> at <a href="http://search.cpan.org/perldoc?Test::Tutorial">http://search.cpan.org/perldoc</a>.</p>
</dd>
<dd>
<p>At Perl Training Australia, we usually add a test based on
<code>Test::Perl::Critic</code> <a href="http://search.cpan.org/perldoc?Test::Perl::Critic">http://search.cpan.org/perldoc</a>
to encourage good coding practices, and <code>Test::Kwalitee</code>
<a href="http://search.cpan.org/perldoc?Test::Kwalittee">http://search.cpan.org/perldoc</a> to catch common
mistakes that are made in distributions.</p>
</dd>
<dd>
<p>Ideally when developing your module, the more tests you have, the better.
If you already have a test suite and you're wondering which parts of
your code are not being tested, you can use the excellent
<code>Devel::Cover</code> tool from <a href="http://search.cpan.org/perldoc?Devel::Cover">http://search.cpan.org/perldoc</a>.</p>
</dd>
</dl>

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